The aim of this project is to provide unequivocal proof for the presence of nuclear imported mRNA in mammalian mitochonria (mt). The proposal is based on the observation that a significant amount of mt polysome-associate RNA has complementarity with nuclear DNA, and that mt in mammalian cells synthesize about 22-24 polypeptides including the tissue specific variant forms. The objective is to determine the genetic origin(s) of 11 or so polypeptides not coded for by the mt genome. Using adsorption on DNA-cellulose and other affinity chromatographic procedures, mRNAs of extra mt genomic origin coding for polypeptides resembling in vivo mt products will be selected out. The extent of importation in Ehrlich ascites, and mouse embryonic liver mt and variations or constancy in other mouse tissues will be determined using molecular hybridization and recombinant DNA procedures. In addition, the nature of information encoded in the extragenomic elements of plasmids will be determined in mouse embryonic mt and compared with the information content and coding properties of similar plasmid structures in other tissues. The overall objective is to understand the genetic basis of tissue-specific variants and the regulatory elements involved in the functional development of mitochrondria.